Topic: Engine health assessment help


47merc68    -- 11-23-2021 @ 2:29 PM
  I recently bought this '47 that has been partially restored, however the engine (and maybe the trany) need some attention. Since the previous owner passed away the records are not real robust. I need some advice on how to assess the health of the engine.

I started by replacing all the coolant hoses and repairing the radiator. I replaced the plugs which yielded much better starting and running. Since my temp gauge is broken, I put in a Bosch mechanical gauge on the passenger side to monitor temps. I tested it in boiling water prior to installing and found it to be about 10 degrees low. When the engine warms up, the 160 degree thermostats seem to open at the right temp which I verified with an infrared thermometer on the sensor housing. Interestingly, the right side warms up much faster than the left. Measuring temps on the sensor housings and heads shows that the left is about 15 degrees cooler than the right. Any thoughts on why this is?
I did a compression test and found that cylinders 1,2,3,4 & 8 were 120 psi; numbers 6 & 7 were 118 psi and number 5 was only 90 psi. My friend said those were good numbers but I am interested in hearing your feedback on this as well as why #5 was lower than the rest. I have not done a vacuum or oil pressure test yet. Thanks for your help and comments.

Also, does anyone know about the "made in Canada" and other nomenclature on the engine head? Does anyone know what the numbers mean on the head?



carcrazy    -- 11-23-2021 @ 5:23 PM
  Things that might be causing the right (passenger's side) bank to run 15 degrees F hotter than the left bank: the thermostat on the hotter side may not be opening fully, the water pump on the hotter side may be less efficient than the other one, there may be some restrictions in the water jacket passages of the hotter side like gaskets or some other partial blockages and the thermostat of the hotter side may be cocked at an angle in the hose and partially blocking coolant flow out of the head.

The compression pressures sound reasonable. Do another compression test making sure to keep the throttle and choke plates wide open during the test. Allow the engine to crank at least 6 revolutions while doing the test and keep cranking until the pressure reaches a maximum.

Do a vacuum test on the engine at idle. If you have approximately 19 inches of vacuum and the reading is steady, you are good to go.


TomO    -- 11-24-2021 @ 7:20 AM
  You have a very nice Mercury convertible. The "C7RA-A " heads are Canadian cast iron heads and have the same properties as the 59AB heads that should be on a USA made engine.

Do a wet compression test on cylinder 5 to see if it is a ring problem or a valve problem. The engine seems to be in very good condition.

Small differences in temperature between the 2 banks are normal and I would not worry about them.

Tom


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